1. Field of the Technology
The technology presented herein relates to an optical-electrical composite transmission device and electronic equipment having the same, and more specifically relates to an optical-electrical composite transmission device suitable for use in, for example, interconnections inside mobile equipment which require downsizing and space saving.
2. Description of the Related Art
In recent years, flexible cables for use in communication between the display section and the operating section of mobile phones are shielded for noise reduction (see JP 2001-119460 A).
However, it is predictable that processing of further high-definition dynamic images entails signal transmission at higher speed, and this higher speed communication causes a problem of electromagnetic wave noise. Moreover, in such application as mobile phone handsets having extremely limited space, shielding the flexible cables as a solution to the problem of electromagnetic waves causes the mobile phones to have complicated configuration and increased dimensions.
Accordingly, for such high speed signal transmission, optical communication has been proposed (see JP 2007-267358 A). However, even in the optical communication, it is necessary to transmit electrical signals to a power source line and a ground line to the display section.
Under these circumstances, an optical-electrical composite cable formed by cladding a power source cable and an optical fiber cable for transmitting optical signals together as one cable (see JP 2002-237226 A), and an optical-electrical composite signal cable using an optical waveguide (see JP H6-281831 A) have been proposed.
It is considered that these optical-electrical composite cables may have problems as stated below:
(i) Difference in material between an electrical signal transmission section and an optical signal transmission section may cause tensile stress and the like, and this stress concentrates on the weaker material;
(ii) Since the electrical signal transmission section is different in material from the optical signal transmission section, a difference in thermal expansion coefficient between the electrical signal transmission section and the optical signal transmission section may potentially deform signal lines at the time of high temperature or low temperature; and
(iii) Manufacture costs of the optical-electrical composite cable are high.
In the case where the electrical signal transmission section is separated from the optical signal transmission section, their lines may be disjoined from each other due to their difference in flexibility and the like. As a result, space saving may become difficult.
Moreover, smaller and thinner mobile phones are being developed in recent years, and foldable mobile phones having a hinged section, for example, are required to make the signal line as small as about 3 mm or less in diameter due to structural limitations.